[Assesing the GRDOSIS Software program as a tool to analyse drug usase by DRGs]. / Evaluación del programa informático GRDOSIS como herramienta de análisis de la utilización de medicamentos por GRD.

OBJECTIVE: To validate the GRDOSIS software program as a tool to calculate Spanish drug weights within diagnosis-related groups (DRGs), and to analyse information used in this calculation. MATERIAL AND METHODS: Information corresponding to a 7-hospital sample is analysed after exchanging data between the minimum basic data set processed by the DRG-grouping program Estación Clínica -3M and unit-dose drug consumption. Data are purged by eliminating cases with an unusual (either long or short) length of stay in each DRG, and both weights and pondered weights are calculated. Data from the 5 most prevalent DRGs are analysed by using the different options provided by the software program, with the aim of detecting intervention points in order to improve results. RESULTS: Extreme case elimination noticeably reduces mean cost per DRG. A reduced group of DRGs represents a high percentage of total cost. Similarly, a reduced number of drugs may represent a high percentage of cost within a given DRG. The use of specific therapeutic groups for specific DRGs is demonstrated, as is the correct use of first-choice drugs versus other therapeutic options within therapeutic groups. An unwarranted variability regarding drug administration dosing and frequency is, however, observed. CONCLUSIONS: The GRDOSIS software program proves itself a powerful tool for both the qualitative (drug usage profiles, dosage) and quantitative (costs) analysis of information originating in a Pharmacy Department

Population estimation of valproic acid clearance in adult patients using routine clinical pharmacokinetic data.

The aim of the present study was to estimate valproic acid (VPA) clearance values for adult patients with epilepsy, using serum concentrations gathered during their routine clinical care. Retrospective steady state serum concentrations data (n=534) collected from 208 adult patients receiving VPA were studied. Data were analysed according to a one-compartment model using the NONMEM program. The influence of VPA daily dose (Dose), gender, age, total body weight (TBW), and comedication with carbamazepine (CBZ), phenytoin (PHT) and phenobarbital (PB) were investigated. The results of the population pharmacokinetics analysis were validated in a group of 30 epileptic patients. The final regression model for VPA clearance (Cl) was: $¿rm Cl¿left (¿rm L/h ¿right )=0¿rm. 004¿times TBW¿times Dose ¿0.304¿¿rm ¿times 1.363¿,¿rm CBZ¿times 1. 541¿,¿rm PHT¿times 1.397¿,¿rm PB.$ The inter-individual variability in VPA clearance, described by a proportional error model, had a variation coefficient (CV) of 23.4% and the residual variability, described using an additive model, was 11.4 mg/L. These results show that VPA clearance increased linearly with TBW, but increases nonlinearly with increasing VPA daily dose. Concomitant administration of CBZ, PHT and PB led to a significant increase in VPA clearance. The model predictions in the validation group were found to have satisfactory precision and bias. In conclusion, inter-individual variability in VPA clearance can be partly explained by TBW, daily dose and bitherapy with CBZ, DPH or PB. Inclusion of these factors allows this variability to be reduced by 37.23% which may be very useful for clinicians when establishing the initial VPA dosage regimen. However, the magnitude of inter-individual plus residual variabilities, remaining in the final model, render these dosage predictions imprecise and justify the need for VPA serum level monitoring in order to individualize dosage regimens more accurately.